CP316: Microprocessor Systems and Interfacing

Introduction to the QwikFlash Development Board (LEDs)

Objectives

• introduction to the development board LEDs
• location of the bi-directional I/O port A

Equipment

• PIC18FXX2 Data Sheet [pdf, 332pp; ©2006 Microchip Technology Inc.]
• QwikFlash board schematic

Procedure

1. On the QwikFlash board, the power LED has a specific function that was covered in first week's lab. The power LED is not under programmer control. The QwikFlash board has four programmer accessible LEDs which have been named: Alive LED, Left LED, Center LED, and Right LED. On the QwikFlash board schematic, locate these LEDs. Sketch the LED circuits in your lab notebook and record any component values. Locate all components on the physical board.
   
   
2. Which microcontroller pins (give pin numbers from schematic) are used to connect to these four LED circuits? How are these pins labeled on the silk artwork on the board?
   
   
3. How is the circuit of the alive LED different from the other three LEDs?
   
   
4. How is this difference related to the difference in pin RA4? In the datasheet, see Table 9-1 PORTA Functions. In the reference manual, see section 11.16 Design Tips, answer 2, part 3 for a more detailed explanation.
   
   
5. General purpose I/O pins are the simplest peripheral devices and are generally called 'ports'. Note that all of the programmable LEDs are connected to PORTA. Port pins may have more than one function; this is called "multiplexing" as the primary function of the pin is multiplexed with alternate functions. On a datasheet, these functions are specified as function 1 / function 2 /.../ function n. The actual pin function for a specific development board is determined by the physical circuitry attached to the pin. If no circuitry is connected to a pin, any of the functions are possible and will be determined when a circuit is attached to the pin. From datasheet Table 9-1 PORTA Functions, note all of the functions for each RAn pin (n = 0, 1, .., 5). From the QwikFlash board schematic, note the function that has been implemented for each of these pins.
   
   Demonstration - explain the components involved in the LED circuitry and their location in the schematic and the physical board.